[PATCH] driver core: fix e1000e ltr bug

YeeLi
2021-06-29T08:21:38Z

In e1000e driver, a PCIe-like device, the max snoop/no-snoop latency
is the upper limit.So, directly compare the size of lat_enc and
max_ltr_enc is incorrect.

In 1000Mbps, 0x8b9 < 0x1003, 189440 ns < 3145728 ns, correct.

In 100Mbps, 0xc3a < 0x1003, 1900544 ns < 3145728 ns, correct.

In 10Mbps, 0xe40 < 0x1003, 18874368 > 3145728, incorrect.

Decoded the lat_enc and max_ltr_enc before compare them is necessary.

Signed-off-by: YeeLi <seven.yi.lee@gmail.com>
---
drivers/net/ethernet/intel/e1000e/ich8lan.c | 23 ++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c b/drivers/net/ethernet/intel/e1000e/ich8lan.c
index 590ad110d383..3bff1b570b76 100644
--- a/drivers/net/ethernet/intel/e1000e/ich8lan.c
+++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c
@@ -986,6 +986,27 @@ static s32 e1000_k1_workaround_lpt_lp(struct e1000_hw *hw, bool link)
return ret_val;
}

+static u32 convert_e1000e_ltr_scale(u32 val)
+{
+ if (val > 5)
+ return 0;
+
+ return 1U << (5 * val);
+}
+
+static u64 decoded_ltr(u32 val)
+{
+ u64 decoded_latency;
+ u32 value;
+ u32 scale;
+
+ value = val & 0x03FF;
+ scale = (val & 0x1C00) >> 10;
+ decoded_latency = value * convert_e1000e_ltr_scale(scale);
+
+ return decoded_latency;
+}
+
/**
* e1000_platform_pm_pch_lpt - Set platform power management values
* @hw: pointer to the HW structure
@@ -1059,7 +1080,7 @@ static s32 e1000_platform_pm_pch_lpt(struct e1000_hw *hw, bool link)
E1000_PCI_LTR_CAP_LPT + 2, &max_nosnoop);
max_ltr_enc = max_t(u16, max_snoop, max_nosnoop);

- if (lat_enc > max_ltr_enc)
+ if (decoded_ltr(lat_enc) > decoded_ltr(max_ltr_enc))
lat_enc = max_ltr_enc;
}

--
2.25.1